Cap assembly and secondary battery

ABSTRACT

The disclosure relates to a cap assembly and a secondary battery. The cap assembly includes: a cap plate including a main portion and a convex portion, wherein the main portion includes a first surface, a second surface and an electrode lead-out hole; an electrode terminal including an extension portion that extends beyond a hole wall of the electrode lead-out hole and extends in a circumferential direction of the electrode lead-out hole to form a ring structure, and the extension portion is arranged on a side of the first surface away from the second surface; and a sealing ring at least partially disposed between the extension portion and the main portion, wherein the convex portion is disposed on the second surface and around the electrode lead-out hole and has a thickness of 0.01 mm to 2 mm, a top surface of the convex portion extends out of the second surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority to Chinese PatentApplication No. 201921066979.7 filed on Jul. 9, 2019, which isincorporated herein by reference in its entirety.

FIELD

The disclosure relates to the technical field of battery, and inparticular to a cap assembly and a secondary battery.

BACKGROUND

Lithium ion secondary batteries have been widely used in the fields ofhybrid vehicles and electric vehicles. This is because it has highenergy, high capacity and high power. The secondary battery includes acap plate, an electrode terminal disposed on the cap plate, a sealingring for sealing the cap plate and the electrode terminal, and a currentcollector connected to the electrode terminal. The cap plate includes anelectrode lead-out hole. The electrode terminal covers the electrodelead-out hole.

SUMMARY

According to embodiments of the disclosure, there is provided a capassembly and a secondary battery. The convex portion of the cap assemblymay increase the strength and rigidity of the section of the mainportion close to the electrode lead-out hole, and reduce the possibilitythat the section is deformed when it is subject to an elastic restoringforce of the sealing ring.

In one aspect, embodiments of the disclosure provide a cap assembly fora secondary battery. The cap assembly includes: a cap plate including amain portion and a convex portion, wherein the main portion includes afirst surface and a second surface that are disposed opposite to eachother in a thickness direction of the main portion and an electrodelead-out hole passing through the first surface and the second surface;an electrode terminal connecting to the main portion and covering theelectrode lead-out hole, wherein the electrode terminal includes anextension portion that extends beyond a hole wall of the electrodelead-out hole in a radial direction of the electrode lead-out hole, theextension portion extends in a circumferential direction of theelectrode lead-out hole to form a ring structure, and the extensionportion is arranged on a side of the first surface away from the secondsurface; and a sealing ring which is at least partially disposed betweenthe extension portion and the main portion to seal the electrodelead-out hole, wherein the convex portion is disposed on the secondsurface and around the electrode lead-out hole, a top surface of theconvex portion extends out of the second surface, and the convex portionhas a thickness of 0.01 mm to 2 mm.

According to an aspect of embodiments of the disclosure, the convexportion includes a ring body disposed around the electrode lead-outhole, or the convex portion includes two or more bosses which areprovided at intervals in the circumferential direction of the electrodelead-out hole.

According to an aspect of embodiments of the disclosure, the top surfaceincludes a planar region and a beveled region.

According to an aspect of embodiments of the disclosure, the capassembly further includes a fixing component, the fixing component iswelded to the cap plate and forms a welding zone, and along the radialdirection, the convex portion exceeds the welding zone or the convexportion is flush with an outermost boundary of the welding zone.

According to an aspect of embodiments of the disclosure, the cap plateincludes a recess surrounding the electrode lead-out hole, the fixingcomponent is welded to a side wall of the recess, a section of the mainportion outside of the recess has a maximum thickness D, and there is amaximum thickness H between a bottom wall of the recess and the topsurface, wherein 0.4≤H/D≤0.9; and/or there is a maximum thickness Hbetween a bottom wall of the recess and the top surface, 0.7 mm≤H≤1.5mm.

According to an aspect of embodiments of the disclosure, the cap plateincludes a recess surrounding the electrode lead-out hole, the fixingcomponent is welded to a side wall of the recess, a portion of thesealing ring between the electrode terminal and the main portion has amaximum compression S, and there is a maximum thickness H between abottom wall of the recess and the top surface, wherein S=kH, and 0<k<1.

According to an aspect of embodiments of the disclosure, along theradial direction, an outer peripheral surface of the sealing ring isarranged outside of an innermost edge of the convex portion.

According to an aspect of embodiments of the disclosure, the secondsurface is smoothly transitioned and connected to an outer surface ofthe convex portion.

According to an aspect of embodiments of the disclosure, the capassembly further includes an insulating component disposed on a side ofthe second surface away from the first surface, the insulating componentincludes a recessed portion in which the convex portion is at leastpartially arranged.

In another aspect, embodiments of the disclosure provide a secondarybattery including: a case including an opening; an electrode assemblydisposed in the case; and a cap assembly according to the aboveembodiments for sealing the opening, wherein the second surface facesthe electrode assembly.

According to another aspect of embodiments of the disclosure, the capassembly further includes an insulating component disposed on a side ofthe second surface away from the first surface, the secondary batteryfurther includes a current collector which includes a main body and anextending portion connected to each other, the main body is arranged ona side of the insulating component away from the second surface, and theextending portion extends into the electrode lead-out hole and isconnected to the electrode terminal; wherein along an axial direction ofthe electrode lead-out hole, there is a first gap between the main bodyand the insulating component; and/or along an axial direction of theelectrode lead-out hole, there is a second gap between the insulatingcomponent and the cap plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical effects of exemplary embodiments ofthe disclosure will be described below with reference to accompanyingdrawings.

FIG. 1 is a structural schematic diagram of a secondary batteryaccording to an embodiment of the disclosure.

FIG. 2 is an exploded structural view of a secondary battery accordingto an embodiment of the disclosure.

FIG. 3 is a structural schematic diagram of a cap plate according to anembodiment of the disclosure.

FIG. 4 is a structural sectional view of a cap assembly according to anembodiment of the disclosure.

FIG. 5 is an enlarged view of a portion A in FIG. 4.

FIG. 6 is an enlarged view of a portion B in FIG. 5.

FIG. 7 is a bottom structural view of a cap plate according to anembodiment of the disclosure.

FIG. 8 is a bottom structural view of a cap plate according to anotherembodiment of the disclosure.

FIG. 9 is a bottom structural view of a cap plate according to anotherembodiment of the disclosure.

FIG. 10 is a partial sectional view of a structure of a cap assemblyaccording to an embodiment of the disclosure.

FIG. 11 is a partial sectional view of a structure of a cap assemblyaccording to another embodiment of the disclosure.

FIG. 12 is a structural sectional view of a sealing ring according to anembodiment of the disclosure.

FIG. 13 is a structural sectional view of a sealing ring according toanother embodiment of the disclosure.

FIG. 14 is a partial exploded structural view of a cap assemblyaccording to an embodiment of the disclosure.

FIG. 15 is a partial sectional view of a structure of a secondarybattery according to an embodiment of the disclosure.

The views are not necessarily plotted in actual proportion in thedrawings.

REFERENCE SIGNS IN THE DRAWINGS

-   -   10 secondary battery;    -   11 case;    -   12 electrode assembly;    -   20 cap assembly;    -   30 cap plate;    -   31 main portion;    -   311 first surface;    -   312 second surface;    -   313 electrode lead-out hole;    -   32 convex portion;    -   321 ring body;    -   322 boss;    -   323 top surface;    -   324 innermost edge;    -   33 recess;    -   331 bottom wall;    -   40 sealing ring;    -   50 terminal assembly;    -   51 fixing component;    -   52 electrode terminal;    -   52 a extension portion;    -   60 insulating component;    -   61 recessed portion;    -   70 current collector;    -   71 main body;    -   72 extending portion;    -   80 first gap;    -   90 second gap;    -   99 welding zone;    -   X radial direction;    -   Y axial direction.

DETAILED DESCRIPTION

Below, embodiments of the disclosure will be further described in detailwith reference to the drawings and embodiments. The detailed descriptionaccording to the embodiments and the accompanying drawings are intendedto exemplary illustrate the principles of the disclosure and are notintended to limit the scope of the disclosure. That is, the disclosureis not limited to the described embodiments.

In the description of the disclosure, it should be noted that, unlessotherwise stated, the meaning of “a plurality” is two or more; theorientation or positional relationship indicated by the terms “upper”,“lower”, “left”, “right”, “inner”, “outer” and the like is merely forthe purpose of describing the disclosure and simplifying thedescription, and is not intended to indicate or imply that the device orcomponent referred to has a particular orientation, is constructed andoperated in a particular orientation, and therefore cannot be understoodto be a limitation of the disclosure. Moreover, the terms “first”,“second”, and the like are configured for descriptive purposes only andare not to be construed as indicating or implying relative importance.

In the description of the disclosure, it should be noted that, unlessotherwise stated, the terms “installation”, “connected to”, and“connected with” are to be understood broadly, and may be, for example,a fixed connection, a disassemble connection, or an integral connection;they can be connected directly or indirectly through an intermediatemedium. The specific meaning of the above terms in the disclosure can beunderstood by the person skilled in the art according to actualcircumstance.

The prior art suffers from at least the following problem: since the capplate and the electrode terminal are hermetically connected by thesealing ring, the compressed portion of the sealing ring produces anelastic restoring force. The elastic restoring force of the sealing ringmay react on the cap plate, so that the portion of the cap plate closeto the electrode lead-out hole may be deformed, which causes a safetyhazard in the use of the secondary battery.

For better understanding of the disclosure, embodiments of thedisclosure will be described below in detail with reference to FIGS. 1to 15.

As shown in FIG. 1 and FIG. 2, a secondary battery 10 according toembodiments of the disclosure includes a case 11, an electrode assembly12 disposed in the case 11 and a cap assembly 20 hermetically connectedto the case 11.

The case 11 according to embodiments of the disclosure is formed in ashape of a rectangular cuboid or in other shapes. The case 11 includesan internal space in which the electrode assembly 12 and electrolyte areaccommodated, and an opening in communication with the internal space.The case 11 may be made of a material such as aluminum, aluminum alloyor plastic.

The electrode assembly 12 according to embodiments of the disclosure mayform a body by stacking a first electrode plate, a second electrodeplate, and a separator between the first electrode plate and the secondelectrode plate together or spirally winding the first electrode plate,the second electrode plate and the separator around a winding axis,wherein the separator is an insulator between the first electrode plateand the second electrode plate. The electrode assembly 12 according tothe embodiment has a flat overall shape with predetermined thickness,height and width. In the embodiment, the description is made byexemplarily taking the first electrode plate as a positive electrodeplate and the second electrode plate as a negative electrode plate.Similarly, in other embodiments, the first electrode plate may be anegative electrode plate, and the second electrode plate may be apositive electrode plate. Furthermore, a positive active material iscoated on a coating region of the positive electrode plate, while anegative active material is coated on a coating region of the negativeelectrode plate. A plurality of uncoated regions extending from thecoating regions of the body serve as tabs. The electrode assembly 12includes two tabs, i.e., a positive tab and a negative tab. The positivetab extends from the coating region of the positive electrode platewhile the negative tab extends from the coating region of the negativeelectrode plate.

As shown in FIG. 2, the cap assembly 20 according to embodiments of thedisclosure includes a cap plate 30 and a terminal assembly 50 connectedto the cap plate 30. The cap plate 30 may cover the opening of the case11 and hermetically connect with the case 11 to enclose the electrodeassembly 12 within the case 11. The cap plate 30 includes an electrodelead-out hole 313. In an embodiment, as shown in FIG. 5, the terminalassembly 50 includes a fixing component 51 and an electrode terminal 52.The electrode terminal 52 is connected to a main portion 31 and coversthe electrode lead-out hole 313. The electrode terminal 52 is connectedto the cap plate 30 through the fixing component 51. The electrodeassembly 12 may be connected to the electrode terminal 52 through acurrent collector. The fixing component 51 includes a hollow cavity inwhich the electrode terminal 52 is accommodated. The hollow cavity ofthe fixing component 51 and the electrode lead-out hole 313 arecorrespondingly disposed in an axial direction Y of the electrodelead-out hole 313.

As shown in FIGS. 3 to 5, the cap plate 30 includes a plate-shaped mainportion 31 and a convex portion 32. The main portion 31 includes a firstsurface 311 and a second surface 312 which are disposed opposite to eachother in its thickness direction. An electrode lead-out hole 313 isprovided in the main portion 31. The electrode lead-out hole 313 passesthrough the first surface 311 and the second surface 312. The thicknessdirection of the main portion 31 is the same as the axial direction Y ofthe electrode lead-out hole 313. The cap plate 30 is hermeticallyconnected to the case 11 through the main portion 31. When the capassembly 20 is applied to a secondary battery, it may be connected tothe case 11 while the second surface 312 of the main portion 31 isadapted to face the electrode assembly 12. Optionally, the cap plate 30is welded to the case 11 through the main portion 31. The convex portion32 is disposed on the second surface 312 of the main portion 31. Theconvex portion 32 is provided around the electrode lead-out hole 313.The convex portion 32 protrudes in the axial direction Y of theelectrode lead-out hole 313 away from the first surface 311. As shown inFIG. 6, a top surface 323 of the convex portion 32 protrudes out of thesecond surface 312. The convex portion 32 has a thickness M of 0.01 mmto 2 mm. The thickness M of the convex portion 32 refers to a maximumvertical distance at which the convex portion 32 protrudes from thesecond surface 312 in the thickness direction. Optionally, the convexportion 32 of the cap plate 30 and the main portion 31 are integrallyformed.

As shown in FIG. 2 and FIG. 5, the cap assembly 20 further includes asealing ring 40. The sealing ring 40 extends in a circumferentialdirection of the electrode lead-out hole 313. A center hole of thesealing ring 40 is disposed corresponding to the electrode lead-out hole313. The electrode terminal 52 includes an extension portion 52 a thatextends beyond a hole wall of the electrode lead-out hole 313 in aradial direction X of the electrode lead-out hole 313. The extensionportion 52 a extends in the circumferential direction of the electrodelead-out hole 313 to form a ring structure. The extension portion 52 ais arranged on a side of the first surface 311 away from the secondsurface 312. When the cap assembly 20 is applied to a secondary battery,the extension portion 52 a is arranged on the side of the main portion31 away from the electrode assembly 12. After the terminal assembly 50is connected and fixed to the cap plate 30, the sealing ring 40 is atleast partially disposed between the extension portion 52 a and the mainportion 31 to seal the electrode lead-out hole 313. The extensionportion 52 a of the electrode terminal 52 and the main portion 31collectively compress a portion of the sealing ring 40 which is disposedbetween the extension portion 52 a and the main portion 31 in the axialdirection Y of the electrode lead-out hole 313. Since the compressedportion of the sealing ring 40 produces an elastic restoring force, theelastic restoring force acts on a section of the main portion 31corresponding to the compressed portion and causes the section to have atrend of deformation in the axial direction Y of the electrode lead-outhole 313. After the convex portion 32 is disposed on the main portion31, the convex portion 32 helps to enhance the deformation resistance ofthe section of the main portion 31 corresponding to the compressedportion, and reduces the possibility of deformation or breakage due tothe elastic restoring force, thereby reducing the possibility of sealfailure.

The cap assembly 20 according to the embodiment of the disclosureincludes a cap plate 30, an electrode terminal 52 and a sealing ring 40.The cap plate 30 includes a main portion 31 and a convex portion 32. Theconvex portion 32 surrounds the electrode lead-out hole 313 disposed inthe main portion 31. The electrode terminal 52 includes an extensionportion 52 a. The portion of the sealing ring 40 disposed between theextension portion 52 a and the main portion 31 produces an elasticrestoring force in the axial direction Y of the electrode lead-out hole313. This elastic restoring force acts on a section of the main portion31 close to the electrode lead-out hole 313. The convex portion 32 mayincrease the strength and rigidity of the section of the main portion 31close to the electrode lead-out hole 313, and reduce the deformationpossibility of the section of the main portion 31 close to the electrodelead-out hole 313 due to a force in the axial direction Y of theelectrode lead-out hole 313, thereby reducing the possibility of sealfailure and improving the safety in use of the secondary battery. Inaddition, since the convex portion 32 may locally increase the strengthand rigidity of the easily deformable region on the main portion 31, thesection of the main portion 31 outside the convex portion 32 may bereduced in size in the thickness direction. Thereby, as compared withthe prior art, the cap plate 30 according to the embodiment includes astructure in which the cap plate 30 is more compact in its thicknessdirection, which is advantageous for increasing the energy density ofthe secondary battery 10.

In one embodiment, the convex portion 32 includes a ring body 321disposed around the electrode lead-out hole 313. The ring body 321extends in the circumferential direction of the electrode lead-out hole313. In one example, as shown in FIG. 7, there is one ring body 321. Thering body 321 and the main portion 31 may be integrally formed by amolding process. In another example, as shown in FIG. 8, there are tworing bodies 321. The two ring bodies 321 have different diameters. Thering body 321 with a smaller diameter among the two ring bodies 321 isdisposed inside the ring body 321 with a larger diameter. The two ringbodies 321 may be arranged coaxially. The number of the ring bodies 321is not limited to one or two, and may be three or more. Three or morering bodies 321 may be arranged in the same way as the two ring bodies321 shown in FIG. 8. The ring body 321 with a smaller diameter isdisposed inside the ring body 321 with a larger diameter. In anotherembodiment, as shown in FIG. 9, the convex portion 32 includes two ormore bosses 322. The two or more bosses 322 are provided at intervals inthe circumferential direction of the electrode lead-out hole 313. Thetwo or more bosses 322 are annularly distributed. Preferably, the two ormore bosses 322 are evenly distributed along the circumferentialdirection of the electrode lead-out holes 313. The second surface 312 ofthe main portion 31 is smoothly transitioned and connected to an outersurface of the convex portion 32, thereby the stress concentrationbetween the convex portion 32 and the main portion 31 in the transitionregion may be reduced.

In one embodiment, as shown in FIG. 5 or FIG. 6, the top surface 323 ofthe convex portion 32 may be generally a planar region. In anotherembodiment, as shown in FIG. 10, the top surface 323 of the convexportion 32 is generally a beveled region. The top surface 323 of theconvex portion 32 is an inner side surface that faces an axis of theelectrode lead-out hole 313. An outer edge of the top surface 323 of theconvex portion 32 away from the axis of the electrode lead-out hole 313is higher than its inner edge close to the axis of the electrodelead-out hole 313. As shown in FIG. 11, the top surface 323 of theconvex portion 32 is generally a beveled region. The top surface 323 ofthe convex portion 32 is an outer side surface that is entirely oppositeto the axis of the electrode lead-out hole 313. The outer edge of thetop surface 323 of the convex portion 32 away from the axis of theelectrode lead-out hole 313 is lower than its inner edge close to theaxis of the electrode lead-out hole 313. In another embodiment, the topsurface 323 of the protrusion 32 includes a planar region and a beveledregion. A portion of the top surface 323 may be a planar region, and theremaining portion is a beveled region.

As shown in FIG. 3, the cap plate 30 includes a recess 33 surroundingthe electrode lead-out hole 313. The recess 33 is recessed from thefirst surface 311 toward the second surface 312. The recess 33 includesa bottom wall 331 and a side wall connected to the bottom wall 331. Thebottom wall 331 of the recess 33 is a surface closest to the secondsurface 312. The terminal assembly 50 is at least partially disposedwithin the recess 33 and covers the electrode lead-out hole 313. Thefixing component 51 is in contact with the bottom wall 331 of the recess33. Since the terminal assembly 50 is disposed in the recess 33, thestructural compactness of the cap assembly 20 in the thickness directionis further improved. Thereby, when the cap assembly 20 according to theembodiment is applied to the secondary battery 10, the energy density ofthe secondary battery 10 may be further improved. The fixing component51 is welded to the cap plate 30. As shown in FIG. 6, the fixingcomponent 51 is welded to a portion of the cap plate 30 which forms theside wall of the recess 33, and forms a welding zone 99. The weldingzone 99 has an innermost boundary close to the axis of the electrodelead-out hole 313 and an outermost boundary away from the axis of theelectrode lead-out hole 313. In one example, along the radial directionX of the electrode lead-out hole 313, the convex portion 32 exceeds thewelding zone 99 such that the outermost edge of the convex portion 32exceeds the outermost boundary of the welding zone 99 and is arranged atoutside of the outermost boundary of the welding zone 99. In this way,at one aspect, the convex portion 32 may reduce the possibility that themain portion 31 is melt through. At another aspect, after the weldingzone 99 is formed, the structural strength of the region of the mainportion 31 close to the welding zone 99 is reduced, and it is beneficialto provide the convex portion 32 to increase the structural strength ofthe region. In another example, along the radial direction X of theelectrode lead-out hole 313, the convex portion 32 is flush with theoutermost boundary of the welding zone 99 such that the outermost edgeof the convex portion 32 is flush with the outermost boundary of thewelding zone 99. Since the recess 33 is disposed on the cap plate 30,the region of the main portion 31 corresponding to the recess 33 isrelatively thinned, such that the thickness of the region is relativelyreduced in the thickness direction and thus the section of the mainportion 31 corresponding to the recess 33 forms a cantilever structure.This section is relatively easily deformed when subjected to an externalforce in the axial direction Y of the electrode lead-out hole 313. Theconvex portion 32 connected to the main portion 31 is disposedcorresponding to the recess 33 disposed on the main portion 31, so thatthe convex portion 32 may improve the deformation resistance of thesection of the main portion 31 corresponding to the recess 33, andreduce the possibility that the section is deformed or broken when it issubject to an external force along the axial direction Y of theelectrode lead-out hole 313.

In one embodiment, as shown in FIG. 6, the section of the main portion31 outside of the recess 33 has a maximum thickness D. There is amaximum thickness H between the bottom wall 331 of the recess 33 and thetop surface 323 of the convex portion 32, wherein 0.4≤H/D≤0.9, and 0.7mm≤H≤1.5 mm. In one example, the section of the main portion 31 outsideof the recess 33 is a structure with a uniform thickness. The portion ofthe main portion 31 outside of the recess 33 has a uniform thickness Dat respective positions, i.e., a vertical distance from the firstsurface 311 to the second surface 312 is D. In another example, the mainportion 31 includes a vent and a fluid inlet. In the axial direction Yof the electrode lead-out hole 313, an outer contour of a projection ofthe vent on the main portion 31 forms a first area, an outer contour ofa projection of the fluid inlet on the main portion 31 forms a secondarea, and an outer contour of a projection of the recess 33 on the mainportion 31 forms a third area. An outer contour of a projection of othersections of the main portion 31 outside of the recess 33, the vent andthe liquid inlet forms a fourth area. The first area, the second area,and the third area are each smaller than the fourth area. The thicknessof other sections of the main portion 31 outside of the recess 33, thevent and the liquid inlet is the maximum thickness D of the main portion31.

In another embodiment, There is a maximum thickness H between the bottomwall 331 of the recess 33 and the top surface 323 of the convex portion32, wherein 0.7 mm≤H≤1.5 mm. In the embodiment, there is no proportionalrelationship between the value of the maximum thickness H and the valueof the maximum thickness D of the section of the main portion 31 outsideof the recess 33. The maximum thickness D of the section of the mainportion 31 outside of the recess 33 may be flexibly selected so long asit may satisfy the thickness requirement.

In an embodiment, as shown in FIG. 2 and FIG. 6, a portion of thesealing ring 40 is disposed in the recess 33 to form a first sealingportion, and other portion is disposed outside of the recess 33 to forma second sealing portion. Both the first sealing portion and the secondsealing portion are annular. Along the radial direction X of theelectrode lead-out hole 313, an outer peripheral surface of the sealingring 40 is arranged outside of an innermost edge 324 of the convexportion 32. The outer peripheral surface of the sealing ring 40 isarranged inside an outermost edge of the convex portion 32. The outerperipheral surface of the sealing ring 40 is a surface away from theaxis of the electrode lead-out hole 313 but extending around the axis ofthe electrode lead-out hole 313. Along the axial direction Y of theelectrode lead-out hole 313, a projection of the innermost edge 324 ofthe convex portion 32 is arranged within a projection of the firstsealing portion. After the terminal assembly 50 is connected and fixedto the cap plate 30, the electrode terminal of the terminal assembly 50and the cap plate 30 collectively press the first sealing portion of thesealing ring 40 in the axial direction Y of the electrode lead-out hole313. Since the first sealing portion will produce an elastic restoringforce when being compressed, the elastic restoring force acts on thesection of the main portion 31 corresponding to the recess 33 such thatthe section will have a tendency to deform in the axial direction Y ofthe electrode drawing hole 313. After the convex portion 32 is disposedon the main portion 31, the convex portion 32 helps to enhance thedeformation resistance of the section of the main portion 31corresponding to the recess 33, and reduces the possibility that thesection of the main portion 31 corresponding to the recess 33 isdeformed or broken due to the elastic restoring force of the firstsealing portion and thus reduces the possibility of seal failure. In oneexample, as shown in FIG. 12, the first sealing portion has a maximumcompression S, and there is a maximum thickness H between the bottomwall 331 of the recess 33 and the top surface 323 of the convex portion32, wherein S=kH, and 0<k<1. Optionally, the maximum thickness H betweenthe bottom wall 331 of the recess 33 and the top surface 323 of theprotrusion 32 is in a range of 0.7 mm≤H≤1.5 mm. The larger an amount ofcompression of the first sealing portion, the larger the elasticrestoring force of the first sealing portion. Thus, the maximumthickness between the bottom wall 331 of the recess 33 and the topsurface 323 of the convex portion 32 shall be correspondingly increasedsuch that the elastic restoring force may be effectively counteract. Theamount of compression refers to a ratio between a recoverable height ofthe first sealing portion in the axial direction Y when the firstsealing portion returns from the compressed state to the free state anda height of the first sealing portion in the free state along the axialdirection Y. The recoverable height is a difference obtained bysubtracting a height S₂ of the first sealing portion in the compressedstate along the axial direction Y from a height S₁ of the first sealingportion in the free state along the axial direction Y. That is to say,the recoverable height is equal to the difference between S₁ and S₂. Sis equal to the ratio of the recoverable height to S₁.

In another embodiment, the sealing ring 40 is entirely disposed withinthe recess 33 of the main portion 31. After the terminal assembly 50 isconnected and fixed to the cap plate 30, the extension portion 52 a ofthe electrode terminal 52 and the cap plate 30 collectively press theentire sealing ring 40 in the axial direction of the electrode lead-outhole 313 to seal the electrode lead-out hole. Since the sealing ring 40produces an elastic restoring force when being compressed, the elasticrestoring force acts on the section of the main portion 31 correspondingto the recess 33 such that the section will have a tendency to deform inthe axial direction of the electrode drawing hole 313. After the convexportion 32 is disposed on the main portion 31, the convex portion 32helps to enhance the deformation resistance of the section of the mainportion 31 corresponding to the recess 33, and reduces the possibilitythat the section of the main portion 31 corresponding to the recess 33is deformed or broken due to the elastic restoring force of the firstsealing portion and thus reduces the possibility of seal failure. In oneexample, as shown in FIG. 13, the sealing ring 40 has a maximumcompression S, and there is a maximum thickness H between the bottomwall 331 of the recess 33 and the top surface 323 of the convex portion32, wherein S=kH, and 0<k<1. Optionally, the maximum thickness H betweenthe bottom wall 331 of the recess 33 and the top surface 323 of theprotrusion 32 is in a range of 0.7 mm≤H≤1.5 mm. The larger an amount ofcompression of the sealing ring 40 is, the larger the elastic restoringforce of the sealing ring 40 will be. Thus, the maximum thicknessbetween the bottom wall 331 of the recess 33 and the top surface 323 ofthe convex portion 32 shall be correspondingly increased such that theelastic restoring force may be effectively counteract. The amount ofcompression refers to a ratio between a recoverable height of thesealing ring 40 in the axial direction Y when the sealing ring 40returns from the compressed state to the free state and a height of thesealing ring 40 in the free state along the axial direction Y. Therecoverable height is a difference obtained by subtracting a height S₂of the sealing ring 40 in the compressed state along the axial directionY from a height S₁ of the sealing ring 40 in the free state along theaxial direction Y. That is to say, the recoverable height is equal tothe difference between S₁ and S₂. S is equal to the ratio of therecoverable height to S₁.

In another embodiment, there is no recess 33 on the main portion 31. Aportion of the sealing ring 40 is disposed between the extension portion52 a of the electrode terminal 52 and the main portion 31 to form afirst sealing portion, and other portion is disposed outside of theextension portion 52 a of the electrode terminal 52 and the main portion31 to form a second sealing portion. After the terminal assembly 50 isconnected and fixed to the cap plate 30, the electrode terminal 52 andthe cap plate 30 collectively compress the first sealing portion of thesealing ring 40 in the axial direction Y of the electrode lead-out hole313. Since the first sealing portion will produce an elastic restoringforce when being compressed, the elastic restoring force acts on themain portion 31 such that the section of the main portion 31corresponding to the first sealing portion will have a tendency todeform in the axial direction Y of the electrode drawing hole 313. Afterthe convex portion 32 is disposed on the main portion 31, the convexportion 32 helps to enhance the deformation resistance of the section ofthe main portion 31 corresponding to the first sealing portion, andreduces the possibility that the section of the main portion 31corresponding to the first sealing portion is deformed or broken due tothe elastic restoring force of the first sealing portion and thusreduces the possibility of seal failure.

In another embodiment, the sealing ring 40 is entirely disposed betweenthe extension portion 52 a of the electrode terminal 52 and the mainportion 31. After the terminal assembly 50 is connected and fixed to thecap plate 30, the extension portion 52 a of the electrode terminal 52and the cap plate 30 collectively compress the sealing ring 40 in theaxial direction Y of the electrode lead-out hole 313. Since the sealingring 40 produces an elastic restoring force when being compressed, theelastic restoring force acts on the main portion 31 such that thesection of the main portion 31 corresponding to the sealing ring 40 willhave a tendency to deform in the axial direction Y of the electrodedrawing hole 313. After the convex portion 32 is disposed on the mainportion 31, the convex portion 32 helps to enhance the deformationresistance of the section of the main portion 31 corresponding to thesealing ring 40, and reduces the possibility that the section of themain portion 31 corresponding to the sealing ring 40 is deformed orbroken due to the elastic restoring force of the sealing ring 40 andthus reduces the possibility of seal failure.

As shown in FIG. 14, the cap assembly 20 further includes an insulatingcomponent 60. The insulating component 60 is disposed on a side of thesecond surface 312 away from the first surface 311. When the capassembly 20 is applied to the secondary battery 10, the insulatingcomponent 60 may isolate the cap plate 30 and the electrode assembly 12.The insulating component 60 and the terminal assembly 50 arerespectively disposed on two sides of the cap plate 30. The insulatingcomponent 60 includes a recessed portion 61 facing a surface of the capplate 30. The convex portion 32 is at least partially arranged in therecessed portion 61. Thereby, in the axial direction Y of the electrodelead-out hole 313, the structural compactness between the insulatingcomponent 60 and the cap plate 30 may be improved, and thus the energydensity of the secondary battery 10 may be improved. In an axialdirection of the electrode lead-out hole 313, a lower surface of theelectrode terminal 52 is higher than a lower surface of the insulatingcomponent 60. Preferably, the convex portion 32 is entirely arrangedwithin the recessed portion 61, and the convex portion 32 and therecessed portion 61 are shaped to match each other. The number of therecessed portions 61 on the insulating component 60 is the same as thenumber of the convex portions 32, and the recessed portions 61 and theconvex portions 32 are provided in one-to-one correspondence.

As shown in FIG. 2 and FIG. 15, the secondary battery further includes acurrent collector 70 for connecting to the tabs. The current collector70 includes a main body 71 and an extending portion 72 that areconnected to each other. The main body 71 is arranged on a side of theinsulating component 60 away from the second surface 312. The extendingportion 72 extends into the electrode lead-out hole 313 and is connectedto the electrode terminal 52. Along the axial direction Y of theelectrode lead-out hole 313, there is a first gap 80 between the mainbody 71 and the insulating component 60; and/or along the axialdirection Y of the electrode lead-out hole 313, there is a second gap 90between the insulating component 60 and the cap plate 30. During theprocess of connecting the extension portion 72 of the current collector70 to the electrode terminal 52, the following case will not happen: themain body 71 is interfered by the insulating component 60 such thatthere is poor contact between the extending portion 72 and the electrodeterminal 52 or the connecting region between the extending portion 72and the electrode terminal 52 is subjected to a large axial tensileforce such that the extension portion 72 and the electrode terminal 52will be easily disconnected. Therefore, the connection reliability ofthe extension portion 72 and the electrode terminal 52 is ensured.

Although the disclosure has been described with reference to thepreferred embodiments, various modifications may be made to thedisclosure and components may be replaced with equivalents withoutdeparting from the scope of the disclosure. In particular, the technicalfeatures mentioned in the various embodiments can be combined in anymanner as long as there is no structural conflict. The disclosure is notlimited to the specific embodiments disclosed herein, but comprises alltechnical solutions falling within the scope of the claims.

What is claimed is:
 1. A cap assembly for a secondary battery,comprising: a cap plate comprising a main portion and a convex portion,wherein the main portion comprises a first surface and a second surfacethat are disposed opposite to each other in a thickness direction of themain portion and an electrode lead-out hole passing through the firstsurface and the second surface; an electrode terminal connecting to themain portion and covering the electrode lead-out hole, wherein theelectrode terminal comprises an extension portion that extends beyond ahole wall of the electrode lead-out hole in a radial direction of theelectrode lead-out hole, the extension portion extends in acircumferential direction of the electrode lead-out hole to form a ringstructure, and the extension portion is arranged on a side of the firstsurface away from the second surface; a sealing ring which is at leastpartially disposed between the extension portion and the main portion toseal the electrode lead-out hole, and a fixing component, wherein theelectrode terminal is connected to the cap plate through the fixingcomponent, wherein the convex portion is disposed on the second surfaceand around the electrode lead-out hole, a top surface of the convexportion extends out of the second surface, and the convex portion has athickness of 0.01 mm to 2 mm; wherein the fixing component is welded tothe cap plate and forms a welding zone, and along the radial direction,the convex portion exceeds the welding zone or the convex portion isflush with an outermost boundary of the welding zone.
 2. The capassembly according to claim 1, wherein the convex portion comprises aring body disposed around the electrode lead-out hole, or the convexportion comprises two or more bosses which are provided at intervals inthe circumferential direction of the electrode lead-out hole.
 3. The capassembly according to claim 1, wherein the top surface comprises aplanar region and a beveled region.
 4. The cap assembly according toclaim 1, wherein the cap plate comprises a recess surrounding theelectrode lead-out hole, the fixing component is welded to a side wallof the recess, a section of the main portion outside of the recess has amaximum thickness D, and there is a maximum thickness H between a bottomwall of the recess and the top surface, wherein 0.4≤H/D≤0.9; and/orthere is a maximum thickness H between a bottom wall of the recess andthe top surface, 0.7 mm≤H≤1.5 mm.
 5. The cap assembly according to claim1, wherein the cap plate comprises a recess surrounding the electrodelead-out hole, the fixing component is welded to a side wall of therecess, a portion of the sealing ring between the electrode terminal andthe main portion has a maximum compression S, and there is a maximumthickness H between a bottom wall of the recess and the top surface,wherein S=kH, and 0<k<1.
 6. The cap assembly according to claim 1,wherein along the radial direction, an outer peripheral surface of thesealing ring is arranged outside of an innermost edge of the convexportion.
 7. The cap assembly according to claim 1, wherein the secondsurface is smoothly transitioned and connected to an outer surface ofthe convex portion.
 8. The cap assembly according to claim 1, whereinthe cap assembly further comprises an insulating component disposed on aside of the second surface away from the first surface, the insulatingcomponent comprises a recessed portion in which the convex portion is atleast partially arranged.
 9. The cap assembly according to claim 4,wherein a portion of the sealing ring between the electrode terminal andthe main portion has a maximum compression S, and there is a maximumthickness H between a bottom wall of the recess and the top surface,wherein S=kH, and 0<k<1.
 10. The cap assembly according to claim 1,wherein along the radial direction, an outer peripheral surface of thesealing ring is arranged outside of an innermost edge of the convexportion.
 11. The cap assembly according to claim 8, wherein in an axialdirection of the electrode lead-out hole, a lower surface of theelectrode terminal is higher than a lower surface of the insulatingcomponent.
 12. The cap assembly according to claim 2, wherein the topsurface comprises a planar region and a beveled region.
 13. The capassembly according to claim 12, wherein the cap assembly furthercomprises a fixing component, the fixing component is welded to the capplate and forms a welding zone, and along the radial direction, theconvex portion exceeds the welding zone or the convex portion is flushwith an outermost boundary of the welding zone.
 14. The cap assemblyaccording to claim 13, wherein the cap plate comprises a recesssurrounding the electrode lead-out hole, the fixing component is weldedto a side wall of the recess, a section of the main portion outside ofthe recess has a maximum thickness D, and there is a maximum thickness Hbetween a bottom wall of the recess and the top surface, wherein0.4≤H/D≤0.9; and/or there is a maximum thickness H between a bottom wallof the recess and the top surface, 0.7 mm≤H≤1.5 mm.
 15. The cap assemblyaccording to claim 13, wherein the cap plate comprises a recesssurrounding the electrode lead-out hole, the fixing component is weldedto a side wall of the recess, a portion of the sealing ring between theelectrode terminal and the main portion has a maximum compression S, andthere is a maximum thickness H between a bottom wall of the recess andthe top surface, wherein S=kH, and 0<k<1.
 16. A secondary battery,comprising: a case comprising an opening; an electrode assembly disposedin the case; and a cap assembly for sealing the opening comprising: acap plate comprising a main portion and a convex portion, wherein themain portion comprises a first surface and a second surface that aredisposed opposite to each other in a thickness direction of the mainportion and an electrode lead-out hole passing through the first surfaceand the second surface; an electrode terminal connecting to the mainportion and covering the electrode lead-out hole, wherein the electrodeterminal comprises an extension portion that extends beyond a hole wallof the electrode lead-out hole in a radial direction of the electrodelead-out hole, the extension portion extends in a circumferentialdirection of the electrode lead-out hole to form a ring structure, andthe extension portion is arranged on a side of the first surface awayfrom the second surface; a sealing ring which is at least partiallydisposed between the extension portion and the main portion to seal theelectrode lead-out hole, and a fixing component, wherein the electrodeterminal is connected to the cap plate through the fixing component,wherein the convex portion is disposed on the second surface and aroundthe electrode lead-out hole, a top surface of the convex portion extendsout of the second surface, and the convex portion has a thickness of0.01 mm to 2 mm, wherein the second surface faces the electrodeassembly; wherein the fixing component is welded to the cap plate andforms a welding zone, and along the radial direction, the convex portionexceeds the welding zone or the convex portion is flush with anoutermost boundary of the welding zone.
 17. The secondary batteryaccording to claim 16, wherein the cap assembly further comprises aninsulating component disposed on a side of the second surface away fromthe first surface, the secondary battery further comprises a currentcollector which comprises a main body and an extending portion connectedto each other, the main body is arranged on a side of the insulatingcomponent away from the second surface, and the extending portionextends into the electrode lead-out hole and is connected to theelectrode terminal; wherein along an axial direction of the electrodelead-out hole, there is a first gap between the main body and theinsulating component; and/or along an axial direction of the electrodelead-out hole, there is a second gap between the insulating componentand the cap plate.
 18. The secondary battery according to claim 17,wherein the convex portion comprises a ring body disposed around theelectrode lead-out hole, or the convex portion comprises two or morebosses which are provided at intervals in the circumferential directionof the electrode lead-out hole.